From patchwork Thu Feb 26 00:31:01 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jorge Ramirez-Ortiz X-Patchwork-Id: 5886001 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 6487EBF440 for ; Thu, 26 Feb 2015 00:41:31 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 5EA4820381 for ; Thu, 26 Feb 2015 00:41:30 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6392D2037F for ; Thu, 26 Feb 2015 00:41:29 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1YQmUE-0001uB-KN; Thu, 26 Feb 2015 00:39:30 +0000 Received: from mail-qc0-f182.google.com ([209.85.216.182]) by bombadil.infradead.org with esmtps (Exim 4.80.1 #2 (Red Hat Linux)) id 1YQmU5-0001f1-0W for linux-arm-kernel@lists.infradead.org; Thu, 26 Feb 2015 00:39:21 +0000 Received: by qcvs11 with SMTP id s11so6014340qcv.11 for ; Wed, 25 Feb 2015 16:38:58 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:to:subject:date:message-id; bh=HpV4G8hkL+Nec3Kr2WIxsO+8i9jwIw41+1FOhAomNnY=; b=Sy0DI9hJyfe98NtXBbicVDq+Mdk/Xkt7SGYygbgx12WCI+Om9XAzpToch4VUkOXsIi sqCY/WIxIu6Z8QRu6ZNdTRXQZ2CKVblAZD8qOZwvVLvbgE9gQ77vME9BnZGlESNiGvkA mFDA7ndu/S5bApXD9V1KAywF4gOUG3pduTgbIAqJNVQOuaab5bI1NEqPHgwPritJOVKG PWRkNDqlwpj+/MgWJ2OODgGRa4cVJ76/jQd6+PDiFOahc3NoNihQ2CpLWuMhmsMAqFWk WiT3cRnpD9JTLO2yF7mwVqSqQ0jVvzrATbIgffe8cFRlRRK5YXKlFvV3H2V8vfAouoRN 6kIg== X-Gm-Message-State: ALoCoQmDUHQpzi6l36pSB4JFdx4b+pJNA/xZt0ypwq4HQbamc+T4rZmVa2qc4udO0+UAn0XvCzj/ X-Received: by 10.140.89.146 with SMTP id v18mr11884170qgd.65.1424910673761; Wed, 25 Feb 2015 16:31:13 -0800 (PST) Received: from localhost.localdomain (cpe-67-247-86-207.rochester.res.rr.com. [67.247.86.207]) by mx.google.com with ESMTPSA id e23sm19371215qhc.21.2015.02.25.16.31.12 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 25 Feb 2015 16:31:13 -0800 (PST) From: Jorge Ramirez-Ortiz To: jorge.ramirez-ortiz@linaro.org, arnd@arndb.de, linux-arm-kernel@lists.infradead.org, robh@kernel.org, viresh.kumar@linaro.org Subject: [PATCH v3] drivers/tty: amba: defer probing DMA availability until hw_init Date: Wed, 25 Feb 2015 19:31:01 -0500 Message-Id: <1424910661-26474-1-git-send-email-jorge.ramirez-ortiz@linaro.org> X-Mailer: git-send-email 1.9.1 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20150225_163921_179623_2B15B83E X-CRM114-Status: GOOD ( 18.61 ) X-Spam-Score: -0.7 (/) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Fix a race condition that happens when device_initcall(pl011_dma_initicall) is executed before all the devices have been probed - this issue was observed on an hisi_6220 SoC (HiKey board from Linaro). The deferred driver probing framework relies on late_initcall to trigger deferred probes so it is just possible that, even with a valid DMA driver ready to be loaded, we fail to synchronize with it. The proposed implementation delays probing of the DMA until the uart device is opened. As hw_init is invoked on port startup and port resume - but the DMA probe is only required once - we avoid calling multiple times using a new field in uart_amba_port to track this scenario. Signed-off-by: Jorge Ramirez-Ortiz --- drivers/tty/serial/amba-pl011.c | 66 ++++++++++------------------------------- 1 file changed, 16 insertions(+), 50 deletions(-) diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c index 8d94c19..3501ccc 100644 --- a/drivers/tty/serial/amba-pl011.c +++ b/drivers/tty/serial/amba-pl011.c @@ -29,6 +29,7 @@ * and hooked into this driver. */ +#define pr_fmt(fmt) "amba-pl011: "fmt #if defined(CONFIG_SERIAL_AMBA_PL011_CONSOLE) && defined(CONFIG_MAGIC_SYSRQ) #define SUPPORT_SYSRQ @@ -164,6 +165,7 @@ struct uart_amba_port { bool using_rx_dma; struct pl011_dmarx_data dmarx; struct pl011_dmatx_data dmatx; + bool dma_probed; #endif }; @@ -261,7 +263,7 @@ static void pl011_sgbuf_free(struct dma_chan *chan, struct pl011_sgbuf *sg, } } -static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port *uap) +static void pl011_dma_probe(struct device *dev, struct uart_amba_port *uap) { /* DMA is the sole user of the platform data right now */ struct amba_pl011_data *plat = dev_get_platdata(uap->port.dev); @@ -275,9 +277,16 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port * struct dma_chan *chan; dma_cap_mask_t mask; - chan = dma_request_slave_channel(dev, "tx"); + uap->dma_probed = true; + + chan = dma_request_slave_channel_reason(dev, "tx"); + if (IS_ERR(chan)) { + if (PTR_ERR(chan) == -EPROBE_DEFER) { + dev_warn(uap->port.dev, "DMA driver not ready\n"); + return; + } + dev_info(uap->port.dev, "no OF or ACPI DMA data\n"); - if (!chan) { /* We need platform data */ if (!plat || !plat->dma_filter) { dev_info(uap->port.dev, "no DMA platform data\n"); @@ -383,54 +392,9 @@ static void pl011_dma_probe_initcall(struct device *dev, struct uart_amba_port * dev_info(uap->port.dev, "DMA channel RX %s\n", dma_chan_name(uap->dmarx.chan)); } -} - -#ifndef MODULE -/* - * Stack up the UARTs and let the above initcall be done at device - * initcall time, because the serial driver is called as an arch - * initcall, and at this time the DMA subsystem is not yet registered. - * At this point the driver will switch over to using DMA where desired. - */ -struct dma_uap { - struct list_head node; - struct uart_amba_port *uap; - struct device *dev; -}; - -static LIST_HEAD(pl011_dma_uarts); - -static int __init pl011_dma_initcall(void) -{ - struct list_head *node, *tmp; - - list_for_each_safe(node, tmp, &pl011_dma_uarts) { - struct dma_uap *dmau = list_entry(node, struct dma_uap, node); - pl011_dma_probe_initcall(dmau->dev, dmau->uap); - list_del(node); - kfree(dmau); - } - return 0; -} - -device_initcall(pl011_dma_initcall); -static void pl011_dma_probe(struct device *dev, struct uart_amba_port *uap) -{ - struct dma_uap *dmau = kzalloc(sizeof(struct dma_uap), GFP_KERNEL); - if (dmau) { - dmau->uap = uap; - dmau->dev = dev; - list_add_tail(&dmau->node, &pl011_dma_uarts); - } + return; } -#else -static void pl011_dma_probe(struct device *dev, struct uart_amba_port *uap) -{ - pl011_dma_probe_initcall(dev, uap); -} -#endif - static void pl011_dma_remove(struct uart_amba_port *uap) { /* TODO: remove the initcall if it has not yet executed */ @@ -1548,6 +1512,9 @@ static int pl011_hwinit(struct uart_port *port) uap->im = readw(uap->port.membase + UART011_IMSC); writew(UART011_RTIM | UART011_RXIM, uap->port.membase + UART011_IMSC); + if (!uap->dma_probed) + pl011_dma_probe(uap->port.dev, uap); + if (dev_get_platdata(uap->port.dev)) { struct amba_pl011_data *plat; @@ -2218,7 +2185,6 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id) uap->port.ops = &amba_pl011_pops; uap->port.flags = UPF_BOOT_AUTOCONF; uap->port.line = i; - pl011_dma_probe(&dev->dev, uap); /* Ensure interrupts from this UART are masked and cleared */ writew(0, uap->port.membase + UART011_IMSC);